Joker

Verified writeups for the Joker machine of Hack The Box

Joker

$ tldr Squid proxy + TFTP → interactive console RCE → tar wildcard cron

·	·
Operating system	Linux
Difficulty	Hard
Vector	Linux privesc
IP	10.10.10.21
Retirement date	2020-08-13
Skills	SQUID Proxy Enumeration UDP Enumeration Abusing TFTP - Getting Squid Proxy Credentials Cracking Hashes Internal port discovery via SQUID Proxy Abusing Interactive Console [RCE] Bypassing iptables rules - UDP Reverse Shell Abusing Sudoers Privilege [Abusing sudoedit - User Pivoting] Abusing Cron Job + TAR Wildcards [Privilege Escalation]

Writeups

Language	Author	Format	Link
🇪🇸 ES	S4vitar	Vídeo	Open
🇬🇧 EN	0xdf	Texto	Open
🇬🇧 EN	IppSec	Vídeo	Open

Skill resources

Curated documentation for each technique listed in the Skills column above. Sources: HackTricks, GTFOBins, PortSwigger, etc.

Skill	Source	Link
Cracking Hashes (hashcat / John)	HackTricks	Open
Port Forwarding / Pivoting	HackTricks	Open
Remote Code Execution (RCE)	HackTricks	Open

Related skills worth mastering

Brute Force / Rate-Limit Bypass · Local File Inclusion (LFI) · Remote File Inclusion (RFI) · Shellshock (CVE-2014-6271)

If you liked this machine, try

• Toby — Linux, Insane
• Unbalanced — Linux, Hard
• Static — Linux, Hard
• CrossFit — Linux, Insane
• Schooled — Linux, Medium

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Last updated: 2026-06-07